This invention relates generally to method and means for reducing the occurrence of bacterial infection caused by (a) implanting a percutaneous lead device in the skin and (b) caused by placement of a catheter in the urinary tract.
Percutaneous lead devices (for example, shunts, cannulae, catheters, wires and other solid or hollow tubular devices) are implanted thru the skin for a variety of medical purposes. These purposes include providing access to arterial and venous blood for the determination of pressures, the collection of samples of blood, the administration of drugs and fluids, etc. Percutaneous lead devices are also used to provide access for flow and pressure monitoring equipment, and for cardiac pacemakers, etc.
Catheters placed in the urinary tract (bladder, kidneys, etc.) are widely used in human and veterinary medicine use of these devices, which are placed through either natural or surgically created openings in the bladder or elsewhere (as in the urinary tract) are complicated by the frequent occurrence of infection resulting from the ingress of bacteria from the external environment onto the surface of these devices. Heretofore, no effective means for the prevention of these infections has been described. The application of antibiotic ointments at the site of entry of the devices has been largely unsuccessful.
In the past, silver has been known to be an oligodynamic metal. The term "oligodynamic" was first used by von Nageli in 1893 to define a material "effective in small quantities." The effect of silver and its salts as an antibacterial agent has long been known. Salts of silver, have been used in washing eyes of newborn babies; silver chloride has been used in treating small wounds and colloidal silver oxide has been used in veterinary medicine. Such uses are not indicative of the oligodynamic character of the metal. Some oligodynamic utilities (characterized by usage of extremely small quantities of silver) are illustrated by treatment of the interior surfaces of glass vessels and filter beds with very small quantity silver salts to control bacterial growth thereon and also to provide a sterile fluid passing therethrough. An excellent treatment of oligodynamic metals and silver can be found in Chapters 24 and 28 of Disinfection Sterilization and Preservation by Lawrence and Black; (Lea and Fibiger; Philadelphia, 1968).
A catheter construction using silver compound is disclosed in U.S. Pat. No. 3,699,956 discovered during a search of prior catheter constructions. The disclosed catheter comprises as an infection-preventing device, a reservoir of liquid adapted to diffuse into surrounding flesh. The inventors disclose the use of solutions including those of silver nitrate and silver sulfadiazine for use in their catheter. However, it appears that the inventors were not suggesting utilization of the oligodynamic effect of silver. All the materials they suggest are known bactericidal materials, but they do not all carry oligodynamic elements. The inventors rely on a flow of these liquid medicines into surrounding flesh at some predetermined release rate rather than a primary contact-type prophylactic action. Thus, the approach of these prior art inventors is substantially different from that of the present inventor. Moreover, the inventors of the prior art, because of their reliance on fluid medication, utilize a highly inconvenient reservoir mechanism which markedly increases the difficulty of initial use by the surgeon and also requires replenishment of fluid medicine on prolonged use in the patient. As will be seen below, utilization of the oligodynamic character makes such a reservoir unnecessary.